FIELD OF THE INVENTION
Conventional image reading apparatus are known to be provided with automatic document feeding devices to improve the efficiency of the original document reading operation. In the aforesaid type of apparatus, the document feeding device sets the original documents on a document platen one sheet at a time. The set original is read via a single scanning operation and the image data are generated. The aforesaid image data are stored in memory, or transmitted to a printing device to be printed on a recording sheet.
In image reading apparatus of the aforesaid type, only a single sheet of the original document can be placed on the document platen. Therefore, in order to read an original document comprising N sheets, the original feeding operation and the scanning operation must be performed N times, i.e., the same number as the number of originals, regardless of the size of said originals.
U.S. Pat. application Nos. 5,005,055 and 5,010,371 have proposed copying apparatus provided with a dual feeding mode for copying wherein two sheets of originals are set on the document platen and both sheets are read in a single scanning operation to improve copying efficiency. In the aforesaid copying apparatus, however, only two sheets of the original can be set on the document platen when the dual feeding mode is selected, even when the size of the originals are less than 1/3 the size of the document platen, i.e., even when the size of the original is such that three sheets can be set on the document platen.